If your hardware has several hard drives, it’s highly recommended that you
specify the exact device to be used during introspection and deployment
as a root device. This is done by setting a root_device property on the
node in Ironic. Please refer to the Ironic root device hints documentation
for more details.

Note that the root device hints should be assigned before both introspection
and deployment. After changing the root device hints you should either re-run
introspection or manually fix the local_gb property for a node:

openstackbaremetalnodeset<UUID>--propertylocal_gb=<NEWVALUE>

Where the new value is calculated as a real disk size in GiB minus 1 GiB to
account for partitioning (the introspection process does this calculation
automatically).

Starting with the Newton release it is possible to autogenerate root
device hints for all nodes instead of setting them one by one. Pass the
--root-device argument to the openstackovercloudnodeconfigureafter a successful introspection. This argument can
accept a device list in the order of preference, for example:

It can also accept one of two strategies: smallest will pick the smallest
device, largest will pick the largest one. By default only disk devices
larger than 4 GiB are considered at all, set the --root-device-minimum-size
argument to change.

Note

Subsequent runs of this command on the same set of nodes does nothing,
as root device hints are already recorded on nodes and are not overwritten.
If you want to change existing root device hints, first remove them manually
as described above.

Note

This command relies on introspection data, so if you change disk devices on
the machines, introspection must be rerun before rerunning this command.

If you don’t know the information required to make a choice, you can use
introspection to figure it out. First start with Introspect Nodes as usual
without setting any root device hints. Then use the stored introspection data
to list all disk devices:

You can use all these fields, except for rotational, for the root device
hints. Note that size should be converted to GiB and that name,
wwn_with_extension and wwn_vendor_extension can only be used starting
with the Mitaka release. Also note that the name field, while convenient,
may be unreliable and change between boots.

Do not forget to re-run the introspection after setting the root device hints.